The standards ISO 7816 and ETS 300 608 (ETSI, code GSM 11.11) define the smart card solutions for the world wide used Global System for Mobile Communications System (GSM) by which information storing is made permanently protected.
FIG. 1 presents a typical ISO 7816 smart card, 85.times.53.times.0.8 mm in size, provided with the eight electrical contacts 15 to the integrated circuit chip inside the card. It also shows one way to encase the encapsulate smart card chip 12. Firstly, the card is laminated from the bottom 10 and middle 11 to which a stepped cavity is produced for the integrated circuit chip 12. Then, the golden or gold plated surfaces 13 are laminated or grown over the stepped side walls and they also form the contact areas 15 which are visible on the surface of the smart card.
According to one manufacturing process the integrated circuit chip 12 of the smart card 1 is glued to the bottom of the cavity and then bonded with gold wire 14 with known methods to the golden contact areas 15 located at the side wail of the cavity. After this the cavity is filled with hardening plastic material so that the contact areas 15 remain visible on the top. According to the ISO 7815 standard the distance between the centre points of the contact areas 15 must be 7.5 mm which means that the width of the integrated circuit chip in the direction B-B' in FIG. 1 can be at most 4 mm.
Other methods for attaching the integrated circuit chip to the smart card are also known. For example, in FIG. 2 a circuit board 20 is used as the substrate and as a contact surface for the integrated circuit chip 12. This circuit board is then embedded into a suitable card base 21 of pre-defined size to form the desired smart card. This structure demands the use of a filling material 22 which also fills the space between the integrated circuit chip 12 and the circuit board 20.
FIG. 3 represent a widely used solution to connect the smart card 30 to a host unit. The contact areas 31 of the smart card 30 are brought in to a mechanical contact with the springs 32 which are electrically connected to the host unit via e.g. a circuit board 33 which is supported by a mechanical frame 34. The frame supports the smart card from the contact side mechanically and the springs 32 press the contact areas 31 with their spring force and an electric contact is produced. According to standards ISO 7816 and ETSI 300 608 the spring force should be less than 0.5 N per each contact.
Previously described solutions have their own advantages and disadvantages. A larger semiconductor chip can be attached to the solution in FIG. 2 than to the solution in FIG. 1, but the costs will rise because of the extra circuit board and costly manufacturing and therefore it is significantly more expensive. There are also other restrictions which limit the present use of smart cards, mostly because they deploy the previously described electric contacts with the host unit. This limits the use of for example the operating voltage to 5 or 3 volts, clock frequency etc. In addition, the electric contact surfaces of the smart card are exposed to touching, rubbing and especially to electrostatic discharge.
Because a reliable electric contact must be accomplished between the smart card and the host unit with the allowed less than 0.5 N force, the structure in FIG. 3 must be very stable and the contact surfaces 31 and 32 must be gold or gold plated. As is known only gold metal can with stand the typical conditions where the smart card is used without oxidizing etc. There fore each contact with the host unit also becomes an extra cost in the manufacturing process.
Previously described solutions use electrical contact between the host unit and the smart card, but also other methods have been introduced. In the publications U.S. Pat. No. 5,206,495, EP 0466 949 A1, DE 42 40 238A1, DE 43 10 334 A1 and U.S. Pat. No. 4,692,604 the contact between the smart card and the host unit is based on a magnetic field through a coil inside the smart card. In the publications EP 0 534 559 A1 and DE 41 38 131 A1 the data transfer is based on electromagnetic radiation in the kHz area.
The closest solution compared to this is the one in GB 2 278085 where both energy and data are transferred between the host and the smart card through optical radiation. The method is however limited to separate photo-voltaic cells which are located at the top of the integrated circuit chip and which convert optical energy into electric current, while the defined current is conducted into the integrated circuit chip through another contact. The optical radiation is focused to the smart card through collimators. The data transfer is suggested to happen with known methods of amplitude modulation. How ever, the application does not include any practical solutions for data transfer and none what so ever for data transfer from the smart card to the host unit. The application also doesn't include any examples of transferring the clock frequency to the smart cards integrated circuit chip. It also leaves open with which values of the parameters the solution is able to work.
This invention has a purpose to present a method with which an information storage and/or processing unit, typically a integrated circuit chip, in a portable device gets energy and the data circuitry it needs without any electric circuitry to the host unit. Then it would be possible to have a portable device which has no conductors between separate parts. Using this method it should be possible to transfer the necessary clock frequency to the integrated circuit chip using optical radiation and to transfer information between the smart card and the host unit at bit-rates up to the said clock frequency.
These goals should be reached with ways that are described in the following independent patent claims.